NAB Plans All-Digital FM Demo in Vegas

The NAB is planning a live demo of all-digital FM HD Radio featuring a total of 12 HD Radio audio services from a single transmitter during the show next month. The demo will feature a Nautel transmitter with Beasley’s KKLZ(FM) serving as the test station.

The demo will be available during regular NAB show hours, according to Nautel officials. The special demo is tied to a session during the Broadcast Engineering and Information Technology Conference that will detail extensive high-power field testing of all-digital FM conducted earlier this year in Las Vegas using the Beasley station. Pilot, the NAB technology and innovation initiative, is hosting the session, “All-Digital FM Field Test Project” on Sunday, April 8, from 1:50–2:10 p.m.

The digital audio channels will be on even-numbered frequencies, so most receivers cannot get these. Attendees can go to the Pilot booth in the Futures Park section of the NAB Show where receivers will be tuned to the even-numbered channels.

Up until now only limited field testing of all-digital HD Radio has been conducted with low transmit power (100W) and reception equipment in non-real world test conditions.

KKLZ’s IBOC signal during the NAB Show will be based on the Nautel all-digital HD multiplex signal composed of three interleaved IBOC sidebands, according to Philipp Schmid, Nautel research engineer.

"To maintain KKLZ’s regular program service, the center sidebands are muted and replaced with the analog FM carrier. The result is two independent IBOC sidebands on both sides of the analog FM signal for a combined bitrate of 394 kbps (over 3.2x standard IBOC capacity), providing up to 12 HD Radio audio services plus the analog FM signal all broadcast by a Nautel GV40 transmitter from the Black Mountain transmission site,” Schmid wrote in an email to Radio World.

The experimental nature of the digital carrier consists of a “several minute-long loops of audio content” and is intentionally placed on the “even” dial positions, according to Schmid.

“The four digital sidebands will be available on 96.0, 96.2, 96.4 and 96.6 MHz that are not normally associated with standard FM radio stations and are receivable on some commonly available HD Radio receivers,” Schmid said.

Meanwhile, KKLZ’s regular FM programming will be available on 96.3 MHz with its regular HD programming suspended in favor of the special signal broadcast under experimental authorization, he explained.

Radio World discussed the recent all-digital FM field tests with David Layer, NAB VP of advanced engineering, for a story in the March 28 issue of Radio World.